JP2004281519A - Plasma processing method and apparatus thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a plasma processing method and apparatus which are capable of subjecting only a very fine region to plasma processing. <P>SOLUTION: A plasma source is equipped with an outer gas exhaust nozzle 6, an inner gas exhaust nozzle 8, and an electrode 14, the plasma source is arranged near to a thin plate 17, a pulse voltage is applied to the electrode 14 as helium and sulfur hexafluoride are fed through the inner gas exhaust nozzle 8 and the outer gas exhaust nozzle 6, respectively, whereby a very fine linear region of the silicon thin plate 17 is subjected to etching. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method and an apparatus for plasma treatment of a minute area.
[0002]
[Prior art]
Generally, when performing a patterning process on an object to be processed represented by a substrate having a thin film formed on a surface, a resist process is used. One example is shown in FIG. 9, first, a photosensitive resist 26 is applied to the surface of the workpiece 25 (FIG. 9A). Next, when the resist 26 is exposed and developed using an exposure machine, the resist 26 can be patterned into a desired shape (FIG. 9B). Then, the workpiece 25 is placed in a vacuum vessel, plasma is generated in the vacuum vessel, and the workpiece 25 is etched using the resist 26 as a mask, and the surface of the workpiece 25 is patterned into a desired shape. (FIG. 9C). Finally, the processing is completed by removing the resist 26 with oxygen plasma or an organic solvent (FIG. 9D).
[0003]
Since the above resist process is suitable for forming a fine pattern with high precision, it has played an important role in the manufacture of electronic devices such as semiconductors. However, there is a disadvantage that the process is complicated.
[0004]
Therefore, a new processing method that does not use a resist process is being studied. As an example, FIG. 10 shows a configuration of a plasma processing apparatus used in a conventional example.
[0005]
FIG. 10 shows a configuration of a plasma processing apparatus in Patent Document 1 in which partial surface treatment can be performed. A voltage is applied from the power supply 31 to one electrode 32. A substrate 35 as an object to be processed is arranged near another electrode 33, and a mixed gas is supplied from a gas inlet 36 for introducing a processing gas to the solid dielectric container, and plasma is generated in the solid dielectric container 34. Then, the active particles are ejected to the substrate 35 from the gas outlet 37 to partially process the substrate 35. That is, partial surface treatment can be performed without using a resist mask. Note that the jig 38 is for connecting one electrode 32 to another electrode 33.
[0006]
[Patent Document 1]
JP-A-9-49083
[Problems to be solved by the invention]
However, in the conventional plasma treatment, there is a problem that the active particles ejected from the gas outlet 37 spread outward, and only a partial surface treatment in a wide range of about 1 mm or more can be performed.
[0008]
An object of the present invention is to provide a plasma processing method and apparatus capable of performing plasma processing only on a very small area in view of the above-described conventional problems.
[0009]
[Means for Solving the Problems]
In the plasma processing method according to the first aspect of the present invention, a plasma source having an inner gas outlet and an outer gas outlet disposed outside the inner gas outlet is brought close to the object, and a part of the object is processed. A plasma processing method for processing, wherein a gas mainly containing an inert gas is jetted toward an object to be processed from an inner gas jet while a reactive gas or an inner gas jet is jetted from an inner gas jet. By emitting a gas that is less likely to be discharged than above and supplying a voltage to an electrode provided in the plasma source or the object to be processed, when generating plasma between the plasma source and the object to be processed, the voltage is reduced to an ON time of zero. It is characterized in that it has a pulse shape of 1 to 10 μs.
[0010]
In the plasma processing method of the first invention of the present application, preferably, the inert gas ejected from the inner gas ejection port is helium, neon, argon, krypton, xenon, or a mixed gas thereof.
[0011]
Preferably, the ON time of the voltage is 0.1 to 1 μs.
[0012]
Preferably, the voltage pulse is direct current, and it is desirable to supply positive and negative direct current pulses substantially alternately. Alternatively, when the voltage pulse is AC, the ON time is t _ON, and the frequency of the _AC is f _AC , f _AC > 1 / t _ON may be satisfied.
[0013]
A plasma processing apparatus according to a second aspect of the present invention includes a plasma source including an inner gas outlet, an outer gas outlet arranged outside the inner gas outlet, an electrode, and an inert gas in the inner gas outlet. An inner gas supply device for supplying a gas mainly composed of a gas, an outer gas supply device for supplying a reactive gas to the outer gas ejection port or a gas which is less likely to be discharged than a gas ejected from the inner gas ejection port, and an electrode or a cover. And a power supply for supplying a pulsed voltage having an ON time of 0.1 to 10 μs to the processing object.
[0014]
In the plasma processing apparatus according to the second aspect of the present invention, it is preferable that the voltage pulse is DC in the power supply, and that the positive and negative DC pulses can be supplied substantially alternately. Alternatively, in the power supply, when the voltage pulse is AC, the ON time is t _ON, and the frequency of the _AC is f _AC , f _AC > 1 / t _ON may be satisfied.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a first embodiment of the present invention will be described with reference to FIGS.
[0016]
FIG. 1 shows an exploded view of the microplasma source. The microplasma source includes an outer plate 1, inner plates 2 and 3, and an outer plate 4 made of ceramic. The outer plates 1 and 4 are provided with an outer gas flow path 5 and an outer gas outlet 6, and the inner plate 2 And 3 are provided with an inner gas passage 7 and an inner gas ejection port 8. The source gas of the gas ejected from the inner gas outlet 8 is supplied from an inner gas supply device (not shown) through an inner gas supply port 9 provided in the outer plate 1 to a through hole 10 provided in the inner plate 2. Via the inner gas flow path 7.
[0017]
The source gas of the gas ejected from the outer gas outlet 6 is supplied from an outer gas supply port 11 provided in the outer plate 1 to a through hole provided in the inner plate 2 by an outer gas supply device (not shown). 12, is guided to the outer gas flow path 5 through a through hole 13 provided in the inner plate 3. Needless to say, the outer gas outlet 6 is disposed outside the inner gas outlet 8. The electrode 14 to which high-frequency power is applied is inserted into an electrode fixing hole 15 provided in the inner plates 2 and 3, and wiring and cooling for supplying high-frequency power are supplied through through holes 16 provided in the outer plates 1 and 4. Done.
[0018]
FIG. 2 shows a plan view of the microplasma source viewed from the gas ejection port side. An outer plate 1, inner plates 2 and 3, and an outer plate 4 are provided, and an outer gas outlet 6 is provided between the outer plate 1 and the inner plate 2 and between the inner plate 3 and the outer plate 4. And 3, an inner gas outlet 8 is provided.
[0019]
FIG. 3 shows a cross section of the thin plate 17 and the microplasma source as the object to be processed, which is cut by a plane perpendicular to the thin plate 17. The microplasma source includes an outer plate 1, inner plates 2 and 3, and an outer plate 4 made of ceramic. The outer plates 1 and 4 are provided with an outer gas flow path 5 and an outer gas outlet 6, and the inner plate 2 And 3 are provided with an inner gas passage 7 and an inner gas ejection port 8. Wiring and cooling to a power supply 18 for supplying a high-frequency voltage are performed on the electrode 14 to which the high-frequency power is applied, through a through hole 16 provided in the outer plates 1 and 4. The inner plates 2 and 3 have a tapered lowermost portion so that a finer linear region can be subjected to plasma processing. The thickness of the fine line formed by the inner gas outlet 8 as the opening of the microplasma source is 0.1 mm. As described above, the processing is performed by bringing the plasma source close to the thin plate 17 as the object to be processed.
[0020]
Also, as is clear from FIGS. 2 and 3, this microplasma source has an opening having a fine linear shape, supplies gas to the outer gas passage 5, communicates with the outer gas passage 5, and The gas is blown out from the outer gas discharge port 6 shallower than the outer gas flow path 5 toward the workpiece 17, and the gas is supplied to the inner gas flow path 7, communicates with the inner gas flow path 7, and The micro plasma is generated by supplying electric power to the electrode 14 while blowing gas toward the workpiece 17 from the inner gas outlet 8 which is shallower than the passage 7. By adopting such a method, the gas supplied from the gas supply device to the outer gas passage 5 or the inner gas passage 7 is first introduced into the outer gas passage 5 or the inner gas passage 7 having a deep and large conductance. And then into the shallow, low conductance outer gas outlet 6 or inner gas outlet 8.
[0021]
In other words, as for the pressure distribution, the inside of the outer gas passage 5 has a higher pressure than the inside of the outer gas outlet 6, and the inside of the inner gas passage 7 has a higher pressure than the inside of the inner gas outlet 8. Therefore, as compared with the case where there is no difference in the depth, the amount and speed of the gas blown out from the outer gas outlet 6 or the inner gas outlet 8 become more uniform in the fine line direction. The magnitude of the conductance of the flow path and the discharge port is expressed by the words "deep" and "shallow", but this is a direction that is approximately perpendicular to the direction of the fine line and approximately parallel to the surface of the workpiece. The width of the flow path or the discharge port is expressed as "deep", and similarly, the flow path or the discharge port in a direction substantially perpendicular to the fine line direction and substantially parallel to the surface of the object to be processed. The narrow width is expressed as "shallow".
[0022]
Further, the high-frequency power supply 18 can supply an AC voltage pulse. As shown in FIG. 4, when the ON time is t _ON and the AC frequency is f _AC , f _AC > 1 / t _ON Can be set to satisfy That is, it is possible to set such that at least one sine waveform is included in one pulse of the voltage.
[0023]
A microplasma source can operate from a few Pa to a few atmospheres, but typically operates at a pressure in the range of about 10 ⁴ Pa to about 3 atmospheres. In particular, operation near the atmospheric pressure is particularly preferable because a strictly closed structure and a special exhaust device are not required and diffusion of plasma and active particles is appropriately suppressed.
[0024]
In a plasma processing apparatus equipped with a microplasma source having such a configuration, helium (He) as an inert gas is supplied from an inner gas outlet, and sulfur hexafluoride (SF ₆ ) is used as a reactive gas from an outer gas outlet. While supplying a pulse voltage as shown in FIG. At this time, t _ON was 0.5 μs (1 / t _ON = 2 MHz) and f _AC was 8 MHz. By performing the plasma processing under such conditions, a minute linear region of the silicon thin plate 17 could be etched. The obtained linear groove width was 65 μm, and a markedly smaller region could be processed as compared with the conventional example.
[0025]
This is because the difference in easiness of discharge between helium and sulfur hexafluoride under a pressure near the atmospheric pressure (helium is much easier to discharge) is used to make the inner gas jet with high helium concentration. Microplasma could be generated only in the vicinity of the outlet 8, and a pulsed voltage was supplied, resulting in a smaller plasma generation area than when a continuous wave AC voltage was supplied. is there. That is, it can be said that stopping the voltage supply in a transient state before the steady state when the continuous wave AC voltage is supplied has an extraordinary effect that has not been achieved in the related art.
[0026]
This will be described in detail with reference to FIG.
[0027]
FIG. 5A shows a state 0.1 μs after supplying a continuous wave AC voltage to the electrodes. Microplasma 19 is generated in the vicinity of the inner gas outlet 8. FIG. 5B shows a state 0.5 μs after supplying a continuous wave AC voltage to the electrodes. A microplasma 19 has developed close to the thin plate 17. FIG. 5C shows a state 10 μs after the continuous wave AC voltage is supplied to the electrodes. A microplasma 19 is formed between the tip of the microplasma source (tips of the inner plates 2 and 3) and the thin plate 17.
[0028]
Note that the size of the microplasma does not increase any more than 10 μs after the continuous wave AC voltage is supplied to the electrode, and the state in FIG. 5C is a steady state when the continuous wave AC voltage is supplied. Is shown. In the present embodiment, since t _{ON is set} to 0.5 μs, the supply of the voltage is stopped in a transient state as shown in FIG. 5B, which results in the supply of a continuous wave AC voltage. This is the reason why the plasma generation region is smaller than in the past, and it is considered that a significantly smaller region could be etched as compared with the conventional example.
[0029]
Reference: Y. See Honda et al. , "Initial Growth Process of Barrier Discharge in Atmospheric Pressure Helium for Glow Discharge Formation", Japanese Journal Applied Physics. 41, Pt. 2, No. 11A (2002) pp. L1256-L1258 describes the result of studying the transient development of the discharge region in a parallel plate type atmospheric pressure plasma source by simulation.
[0030]
In FIG. 6 shown in this document, the horizontal axis is the radial position of the circular parallel flat plate, and the vertical axis is the electron density. As can be seen from FIG. 6, it is understood that the plasma gradually spreads in 1.4 μs after the start of the voltage supply. Although this study does not deny that it was a big hint leading to the present invention, this document does not mention the processing of minute regions at all, and the present invention restricts the plasma generation region to a smaller region. In addition, it has also added a device to eject the inert gas and the reactive gas from the inner and outer gas outlets respectively, and even if this document is combined with any other known technology, the present invention can be easily achieved. I can't imagine.
[0031]
In addition, Patent Literature 1 described in the related art also describes application of a pulsed voltage, but this is intended solely to prevent abnormal discharge (arc), and narrows the discharge region. It is not mentioned. That is, it is not considered that the present invention can be easily achieved by combining Patent Document 1 with any other known technology. Even if a pulse-like voltage is applied in the configuration of Patent Literature 1, arc discharge can be prevented, but the discharge region is widened, and it is impossible to process only a very small region. TECHNICAL FIELD The present invention relates to a technology capable of processing an area smaller than 1 mm, and further, smaller than 0.1 mm.
[0032]
In the embodiment of the present invention described above, the case where four ceramic plates are used as the plasma source is exemplified. However, a capillary type such as a parallel plate type capillary type or an inductive coupling type capillary type, a micro gap type, and an induction type. Various plasma sources, such as a coupled tube type, can be used. In particular, in the type using the knife-edge-shaped electrode 24 as shown in FIG. 7, since the distance between the electrode and the object to be processed is short, extremely high-density plasma is formed in a minute portion. Therefore, the present invention is particularly effective. In FIG. 7, the plasma source is composed of an outer plate 20, inner plates 21 and 22, an outer plate 23, and an electrode 24 made of ceramic. The inner plates 21 and 22 are provided with an inner gas passage 7 and an inner gas outlet 8. The lowermost portion of the electrode 24 has a knife-edge shape so that a fine linear region can be subjected to plasma processing.
[0033]
Although the case where the plasma processing is performed on a fine linear region is illustrated, the present invention is also applicable to the case where a fine point region is processed. In this case, the inner gas outlet is an annular shape provided around a minute point-like or minute point-like solid, and the outer gas outlet surrounds the inner gas outlet outside the inner gas outlet. What is necessary is just to provide in the annular shape provided by.
[0034]
Further, by supplying a pulsed voltage to the object to be processed, it is possible to enhance the effect of attracting ions in the plasma. In this case, the electrode may be grounded, or the electrode may be kept at a floating potential. Alternatively, a second electrode may be provided on the side opposite to the plasma source across the object to be processed, the second electrode may be grounded, or a pulsed voltage may be supplied to the second electrode. Is also good. The second electrode has an effect of concentrating an electric field when the object to be processed is a dielectric, and has an advantage that it is not necessary to provide a contact to the object to be processed when the object includes a conductor.
[0035]
Although the case where the plasma is generated using a pulsed high-frequency (AC) voltage has been described as an example, a high-frequency power of several hundred kHz to several GHz can be used as the frequency of the AC voltage. However, the voltage needs to be pulsed with an ON time of 0.1 to 10 μs. In order to control the ON time to less than 0.1 μs, there is an inconvenience that the voltage supply circuit requires special measures so that the waveform does not become blunt. Plasma cannot be generated in a limited manner. More preferably, the ON time of the voltage is preferably 0.1 to 1 μs. If the ON time is 1 μs or less, it is possible to generate plasma in a limited area that is extremely small as compared with the steady state.
[0036]
It is also possible that the voltage pulse is DC, and positive and negative DC pulses are supplied substantially alternately. In this case as well, the voltage needs to be pulsed with an ON time of 0.1 to 10 μs. More preferably, the ON time of the voltage is preferably 0.1 to 1 μs. FIG. 8 shows an example of the voltage waveform. Although a positive or negative DC pulse may be continuously supplied, discharge occurs only at the first pulse whose polarity is reversed due to charging, so that in this case, the positive or negative It is considered that DC pulses are supplied alternately.
[0037]
Further, it is desirable that the OFF time of the pulse voltage is set to be equal to or longer than the time required for the generated plasma to be almost completely extinguished and to be as short as possible to improve the processing speed. The time is preferably approximately 0.5 μs to 100 μs. More preferably, the OFF time of the pulse voltage is preferably 1 μs to 10 μs.
[0038]
In addition, although the case where the helium gas is ejected from the inner gas ejection port toward the object to be processed is exemplified, the gas ejected from the inner gas ejection port needs to be a gas mainly composed of an inert gas. This is because, in general, a gas mainly composed of an inert gas has a property that it is more easily converted to plasma under a pressure near the atmospheric pressure than other gases.
[0039]
In addition, although the case where the sulfur hexafluoride gas is ejected from the outer gas ejection port is exemplified, the reactive gas or the gas which is less likely to be discharged than the gas ejected from the inner gas ejection port is ejected from the outer gas ejection port. is necessary. The method of supplying a pulsed voltage has the property of generating a stable glow discharge, so if an easily dischargeable gas such as an inert gas is ejected from the outer gas ejection port, the plasma spreads over a wide range. There is an inconvenience that it is easy to do. The inert gas supplied from the inner gas outlet is preferably helium, neon, argon, krypton, xenon, or a mixed gas thereof. Helium gas is a gas that easily generates a stable glow discharge near the atmospheric pressure, and is particularly preferable. The gas supplied from the outer gas outlet is preferably a gas mainly containing a gas other than helium, neon, argon, krypton, or xenon, and an etching gas containing halogen such as fluorine, chlorine, and bromine, and TEOS. Can be selected from deposition gases typified by organic silanes and gases that are difficult to discharge, such as oxygen and nitrogen, depending on the processing.
[0040]
Further, when the voltage pulse is AC, the ON time is t _ON , and the AC frequency is f _AC , t _ON is 0.5 μs (1 / t _ON = 2 MHz), and f _AC is 8 MHz. However, it is preferable that f _AC > 1 / t _ON be satisfied. It is extremely difficult to form a waveform that does not satisfy f _AC > 1 / t _ON . It is more desirable that f _AC > 10 / t _ON be satisfied. When f _AC is smaller than 10 / t _ON , the side band is generated far apart from the center frequency f _{AC at} a voltage as viewed as pulse-modulated _AC, so that it is difficult to achieve impedance matching. In order to ensure good impedance matching and suppress reflected power, it is better that f _AC is larger than 1 / t _ON .
[0041]
【The invention's effect】
As is apparent from the above description, according to the plasma processing method of the first invention of the present application, the plasma source having the inner gas outlet and the outer gas outlet arranged outside the inner gas outlet is processed. A plasma processing method for processing a part of an object to be processed in close proximity to an object, wherein a gas mainly composed of an inert gas is ejected toward an object to be processed from an inner gas outlet and a reaction is performed from an outer gas outlet. The gas between the plasma source and the object to be processed is generated by ejecting a gas that is less likely to be discharged than the neutral gas or the gas ejected from the inner gas outlet, and supplying a voltage to the electrode or the object to be processed provided in the plasma source. When the voltage is generated, the voltage is pulsed with an ON time of 0.1 to 10 μs, so that plasma processing can be performed only on an extremely small area.
[0042]
Further, according to the plasma processing apparatus of the second invention of the present application, a plasma source including an inner gas jet, an outer gas jet arranged outside the inner gas jet, an electrode, An inner gas supply device for supplying a gas mainly composed of an inert gas to an outlet; and an outer gas supply device for supplying a reactive gas or a gas which is less likely to be discharged than a gas ejected from the inner gas ejection port to an outer gas ejection port. Since a power supply for supplying a pulsed voltage having an ON time of 0.1 to 10 μs to the electrode or the object to be processed is provided, plasma processing can be performed only on an extremely small area.
[Brief description of the drawings]
FIG. 1 is an exploded view of a plasma source used in an embodiment of the present invention. FIG. 2 is a plan view of a plasma source used in an embodiment of the present invention. FIG. FIG. 4 is a view showing an AC voltage pulse waveform in the embodiment of the present invention. FIG. 5 is a sectional view showing a transient state of plasma generation. FIG. 6 is a view showing a simulation result of a transient development of a discharge region. FIG. 7 is a cross-sectional view of a plasma processing apparatus used in an embodiment of the present invention. FIG. 8 is a view showing a DC voltage pulse waveform in the embodiment of the present invention. FIG. 9 is a view showing a resist process used in a conventional example. FIG. 10 is a sectional view showing a process. FIG. 10 is a sectional view of a plasma processing apparatus used in a conventional example.
REFERENCE SIGNS LIST 1 outer plate 2 inner plate 3 inner plate 4 outer plate 5 outer gas flow path 6 outer gas jet 7 inner gas flow 8 inner gas jet 14 electrode 16 through hole 17 thin plate 18 power supply

Claims (8)

A plasma processing method for processing a part of an object to be processed by bringing a plasma source having an inner gas jet and an outer gas jet arranged outside the inner gas jet close to the object, comprising: A gas mainly composed of an inert gas is ejected from an ejection port toward an object to be processed, and a reactive gas or a gas which is harder to discharge than a gas ejected from an inner gas ejection port is ejected from an outer gas ejection port, and plasma is generated. When generating a plasma between the plasma source and the object by supplying a voltage to the electrode or the object provided in the source, the voltage is pulsed with an ON time of 0.1 to 10 μs. A plasma processing method characterized by the above-mentioned. 2. The plasma processing method according to claim 1, wherein the inert gas ejected from the inner gas ejection port is helium, neon, argon, krypton, xenon, or a mixed gas thereof. 2. The plasma processing method according to claim 1, wherein the ON time of the voltage is 0.1 to 1 [mu] s. 2. The plasma processing method according to claim 1, wherein the voltage pulse is DC, and positive and negative DC pulses are supplied substantially alternately. 2. The plasma processing method according to claim 1, wherein f _AC > 1 / t _ON is satisfied when the voltage pulse is alternating current, the ON time is t _ON, and the frequency of the alternating current is f _AC . A plasma source including an inner gas jet, an outer gas jet disposed outside the inner gas jet, and an electrode, and an inner gas for supplying a gas mainly composed of an inert gas to the inner gas jet. A supply device, an outer gas supply device that supplies a reactive gas to the outer gas outlet or a gas that is less likely to be discharged than a gas ejected from the inner gas outlet, and an ON time of 0.1 to 10 μs to the electrode or the workpiece. And a power supply for supplying a pulsed voltage. 7. The plasma processing apparatus according to claim 6, wherein in the power supply, the voltage pulse is DC, and positive and negative DC pulses can be supplied substantially alternately. 7. The power supply according to claim 6, wherein f _AC > 1 / t _ON can be satisfied when the voltage pulse is alternating current, the ON time is t _ON, and the frequency of the alternating current is f _AC. Plasma processing equipment.

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